The Organic Light Emitting Display (OLED) possesses many outstanding properties of self-illumination, low driving voltage, high luminescence efficiency, short response time, high clarity and contrast, near 180° view angle, wide range of working temperature, applicability of flexible display and large scale full color display. The OLED is considered as the most potential display device.
The OLED can be categorized into two major types according to the driving methods, which are the Passive Matrix OLED (PMOLED) and the Active Matrix OLED (AMOLED), i.e. two types of the direct addressing and the Thin Film Transistor (TFT) matrix addressing. The AMOLED comprises pixels arranged in array and belongs to active display type, which has high lighting efficiency and is generally utilized for the large scale display devices of high resolution.
With the development of the display technology, the requirements of the people to the display qualities of the display device, such as the display brightness, the color reduction, the richness of the image color gets higher and higher. The display merely utilizing the red, green and blue, three primary colors can no longer satisfy the requirements of the people to the display device. Thereafter, the four colors display device having red, green, blue, white four colors is proposed. One white sub pixel is added in each pixel for forming the RGBW pixel structure constructed by the red sub pixel R, the green sub pixel G, the blue sub pixel B and the white sub pixel W. In the same display image, the display device utilizing the RGBW pixel structure has the display brightness, the color reduction and richer image colors with higher quality than the display device utilizing the RGB pixel structure, and is pursued by the consumers.
However, the data driving circuit of the AMOLED display device according to prior art generally comprises only three sets of independent gamma voltages, i.e. the red, the green and the blue gamma voltages. Because the output of the data driving circuit is fixed for corresponding the circular permutation of the red, green, blue sub pixels, and as being applied in the RGBW four colors display device, it will cause the corresponding error of the blue gamma voltage. Therefore, it is required to independently process the white gamma voltage corresponding to the white sub pixel. As shown in FIG. 1, the white sub pixels are all coupled to the second data driving circuit 202 above the display panel 100 for process, and the first data driving circuit 201 under the display panel 100 still processes the red, the green and the blue sub pixels. However, the additional data driving circuit will increase the cost, and meanwhile, the data driving circuit of the AMOLED display device according to prior art generally is one way output, and cannot receives the compensation signal transmitted from the side of the display panel 100, and the function is solo.